The objective of this research is the development and utilization of assays to detect the presence of 0.5 to 1% leukemic cells in the total nucleated bone marrow cell population by utilizing the differential rate of synthesis of the template independent DNA polymerase terminal deoxynucleotidyl transferase (TdT). Rather than utilizing the already well-characterized steady-state measurements embodies in biochemical, immunofluoresecent, and antibody affinity assays, the dynamic quality of rate of TdT biosynthesis will be utilized to discriminate between normal and leukemic TdT-positive marrow poulations. The biosynthesis rate by leukemic cells is measurably greater than the rate of synthesis by equivalent numbers of normal TdT positive cells in bone marrow. As a further refinement, cDNA probes for human TdT-specific message will be utilized to establish correlations beweeen rate of RNA synthesis, steady-state levels of mRNA, and protein biosynthesis. These measurements will be extended to heterogeneous model populations and clinical samples. The prognostic value of these assays will be determned by applying the assays to routine clincal samples from leukemic patients in treatment, or off treatment and in remission, who have had, or might develop, TdT-positive disease.